Tarpaulin cover systems are commonly used to cover cargo being transported by truck, train, ship, and other vehicles. It is often desirable to cover cargo to protect it from the elements. It may also be desirable to shield the cargo from view.
Cargo that is to be transported may be positioned directly on a vehicle, such as on a truck or trailer bed, or on a rail car. Alternatively, the cargo may first be positioned on a shipping base, such as a shipping or cargo pallet. The shipping base may then be placed on or in the vehicle for transport. The term “base structure” will hereinafter be used to refer to both vehicles and shipping bases. In either instance, it is often desirable to cover the cargo being transported.
Tarpaulin cover systems are particularly common in the trucking industry. One type of shipping configuration comprises a fully enclosed and rigid cargo area. Most of these cargo areas have one or more doors in the enclosure for loading and unloading the cargo. In particular, many trucks or trailers have an opening at their rear end for this purpose. However, such fully enclosed and permanent cargo areas are not well suited for the loading and unloading of certain types of cargo. For example, very large or very heavy items are most easily loaded onto a vehicle, trailer, or base from the top or the side using a crane, forklift or other lifting device. Therefore such large or heavy items are more easily loaded onto a vehicle, trailer, or base having no sidewalls or no roof. Flatbed trucks and trailers are well adapted to carry such loads. However, as discussed above, it is often desirable to cover the loaded cargo during transport, as well as during storage. Tarpaulin cover systems provide an attractive solution as they can be quickly and easily retracted or removed to expose the entire cargo area during loading.
Tarpaulin cover systems are known in the art. For example, flexible tarpaulin systems for highway trailers have been disclosed in U.S. Pat. No. 5,152,575 to DeMonte et al., U.S. Pat. No. 5,538,313 to Henning, and U.S. Pat. No. 6,511,117 to Henning.
Retractable tarpaulin systems can come in a flat-top style, as taught by the two Henning patents, or in a peaked style, as taught by DeMonte. An increasingly common style of flexible cover system comprises a plurality of bows that support a flexible cover. The bows, and thus the cover, are moveable, typically along the length of the base or vehicle, and may be retracted in an accordion-like manner to expose a cargo area. The lower ends of each bow typically comprise sliding means, such as one or more wheels or rollers, which ride in or on a pair of tracks or rails on the base or vehicle.
It is important that the tarpaulin cover in retractable bow-style cover systems be fully stretched-out when the cover is in the extended position. In other words, it is important that tension be maintained in the tarp cover system. This is particularly significant for cover systems that are exposed to high winds or fast-moving air, such as cover systems positioned on vehicles. Firstly, applying and maintaining tension in the cover reduces the severity of flapping in the cover caused by the passing air or wind. A reduction in flapping reduces the material fatigue in the cover and in the bows, and therefore prolongs the service life of these parts. A reduction in flapping also reduces the amount of noise emitted and provides for a quieter ride. Secondly, a taut cover reduces the aerodynamic drag of the cover system. This likely increases the fuel or energy economy of the vehicle transporting the cover system. For the aforementioned reasons, it is desirable to have a satisfactory and substantially uniform tension in the flexible cover.
Tensioning devices and systems for sliding systems covers are also known in the art. Many existing systems involve the application of a force to the front-most or rear-most bow in order to fully stretch out the cover. For example, one such system is disclosed in U.S. Pat. No. 6,616,211 to Cramaro, which uses a crank and a lever that are connected to rear-most bow of the moveable tarpaulin framework. The crank is first rotated to move the lever into a catch position, and then counter-rotated to further extend the framework, which in turn stretches-out the cover.
However, known systems such as the one disclosed by Cramaro suffer from a number of shortcomings. In particular, the tensioning force applied in many existing systems is applied to a front-most or a rear-most bow at the lower ends of the bow. As a result, a satisfactory degree of tension can be applied and maintained in the lower side portions of the cover. However, the resultant tension in the upper side portions and the top portion of the cover will be lower than the tension achieved in the lower side portions. This difference can be at least partially attributed to the flexibility of the parts of the covering system, and in particular of the front-most or rear-most bow.
Existing tensioning devices and systems suffer from further shortcomings. Many systems are heavy or bulky, or both, and are therefore difficult to install and operate. Some systems are inefficient in that they require a significant amount of physical effort or time to achieve the desired degree of tension in the cover.
For the foregoing reasons, it can be appreciated that a need exists for a tarp tensioning and locking device that produces a satisfactory amount of tension in the entire cover, including the side portions and top portion of the cover. It is also desirable that the device be compact, lightweight, and easy to use.